This application claims the priority of German Application No. 101 59 069.5, filed Dec. 1, 2001, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method for operating an electronic controller of a motor vehicle.
The operation of modern motor vehicles or of engines for driving them is usually controlled by an electronic controller. For this purpose, the controller is provided with a plurality of input signals which are usually supplied by associated sensors. These signals are further processed in the controller. Output signals which influence the operation of the motor vehicle and/or of the associated engine are generated as a function of the result of this signal processing. Typical output signals are control signals which relate to the driving state of the motor vehicle or the fuel injection. These output signals influence, for example, the rotational speed or the output power of the engine. For the reliability and the quality of the operation of the motor vehicle or of the engine it is important for the controller to be operated with reliable and precise signal processing.
The object of the present invention is to provide a method for improved operation of an electronic controller of a motor vehicle and/or of a motor vehicle engine.
According to the invention, the signal processing of the controller includes a filtering operation, carried out as a function of the operating state of the motor vehicle and/or of the engine. According to the invention, the decision as to whether or not filtering is to be carried out for a specific signal is taken as a function of the operating state of the motor vehicle and/or of the engine. If, for example, it is known, or there is a risk, that an operating parameter of the engine, for example the rotational speed of the engine, has a disruptive influence on a signal, for example the signal of a sensor, within a specific value range, it is thus possible to provide a signal. The filtering operation for this signal, which filtering operation is activated if the respective engine operating parameter is in this specified value range. Because the filtering operation may be associated with a loss of information or a loss of sensitivity, it is advantageous to dispense with the filtering of the signals when the respective parameter leaves the critical value range, and thus when the disruptive influence is eliminated. Therefore the unfiltered signal is again processed. It is particularly advantageous to influence the type of filtering or the characteristic values which characterize the filtering, in the controller. This influence advantageously enables the signal processing to be adapted to the dynamics of the respective operating states. In this way, for example variables which characterize the operation of an internal combustion engine, such as the rotational speed, fuel injection conditions, torque or partial vacuum of the intake manifold in the idling mode, change comparatively slowly while they change comparatively quickly during the acceleration processes of the respective motor vehicle. Variables which determine the operating state of the entire motor vehicle change in a comparable way. Depending on the operating state of the motor vehicle, these variables, for example the travel speed, the pressure of the fuel in the supply system or the like, may change more or less quickly. By means of a filtering operation, adapted to the operating state, during the signal processing it is possible to control the operation of the motor vehicle and/or of the engine in an optimum way at any time. For this purpose, the filtering operation is carried out at an expediently selected point on the signal path. For example, the filtering operation can be carried out directly on the input signal which is received in the controller, or after a logic operation has been performed on a plurality of signals. Here, according to the invention, a filtering operation is understood in a general way as the selective influencing of the amplitude spectrum of a signal. Depending on the type of signal, the filtering may achieve various advantages or objectives. For example, the removal, gating out or reduction of interference or extraneous frequency components of the signal, such as noise, interference peaks or the like, may be aimed at, or, in the case of an output signal of the engine controller, the dynamics of the signal can be adapted to the inertia of the component actuated with it.
In a refinement of the invention, the filtering operation includes a low-pass filtering operation. By means of a low-pass filtering operation it is possible, in particular, to smooth a signal or to remove undesired interference peaks, as a result of which a more reliable and precise control of the operation of the motor vehicle or of the engine is made possible. Relatively large frequency components of a signal are preferably then removed or attenuated by means of the low-pass filtering if procedures, which may vary slowly, are sensed or controlled by means of the signal on the basis of the current operating state of the motor vehicle or of the engine. If the respective process becomes variable more quickly as a result of a change of the operating state, it is then possible to react by, for example, reducing the attenuation or other characteristic values of the low-pass filtering operation, so that the variables which change quickly over their time profile can then be reliably registered.
In a further refinement of the invention, a cut-off frequency and/or attenuation operation which is assigned to the low-pass filtering operation are selected as a function of the operating state of the internal combustion engine. Cut-off frequency is to be understood as the frequency above which attenuation ideally becomes effective or changes in accordance with the filter characteristic. If, for example in the case of a low-pass filtering operation, a first-order delay element is used for smoothing a signal, depending on the dynamics of the current motor vehicle operation or engine operation the cut-off frequency can be increased or decreased, and the frequency range in which the signal smoothing takes place can be adapted to the current conditions. In a similar manner, by switching over to a different type of signal filtering it is possible to increase or reduce the degree of attenuation in a specific frequency range, as required and as a function of the operating state of the motor vehicle or engine.
In a further refinement of the invention, the filtering operation is carried out when determining and/or processing a characteristic variable which is assigned to an exhaust gas purification device of the motor vehicle. The optimum operational capability of exhaust gas purification devices have a particular significance due to the tightening of limiting values for pollutants. Exhaust gas purification devices of motor vehicles with internal combustion engines frequently have fragile, fault-prone or sensitive sensors whose signals have to be conditioned and processed in compliance with the situation as satisfactorily as possible so that the required quality of the exhaust gas purification is obtained. Some examples include frequency and amplitude control and the regulation of the air/fuel ratio in spark ignition engines, which are equipped with three-way catalytic converters. In this case, lambda probes are used in the exhaust gas purification system to sense the air/fuel ratio of the exhaust gas, and the combustion is controlled or regulated by the engine controller. The reliability during signal processing, in particular of weak or fault-prone signals, is of great importance for the best possible purification of the exhaust gases here. A further example is the operation of nitrogen oxide storage-type catalytic converters which have to be regenerated from time to time by changing from lean combustion to rich combustion. For this process to be controlled in an optimum way it is necessary to perform satisfactory signal conditioning which is advantageously achieved by filtering as a function of the operating state during the signal processing of the engine controller.
In a further refinement of the invention, the filtering operation is carried out when determining and/or processing a variable assigned to a charge of a particle filter arranged in an exhaust gas purification device of an engine which is embodied in particular as an autoignition internal combustion engine. Motor vehicle engines which are embodied in particular as autoignition internal combustion engines or as diesel engines can be equipped with a particle filter in the exhaust gas purification device in order to reduce the emission of particles. As a result of the accumulation of particles, the particle charge of these filters increases over the course of time so that these filters are regenerated at recurring intervals, preferably by burning off the collected particles of soot. The charge is typically continuously determined on the basis of a measurement of pressure or of a measurement of pressure differences. Here, the signal which is supplied by a pressure sensor is transmitted to the controller and the current charge of the particle filter is usually determined by logic linking to other calculated signals, or signals determined in some other way, such as exhaust gas temperature, air throughput rate, fuel throughput rate, rotational speed and the like. The signal filtering operation according to the invention when determining the charge of the particle filter as a function of the operating state of the internal combustion engine improves the precision of the determined charge value in a particularly advantageous way. On the one hand the slowly varying process of the increasing particle filter charge can be reliably tracked and on the other hand, the charge value which changes relatively quickly during the regeneration of the particle filter, can be determined more precisely. This improves the detection of the need for particle filter regeneration, and the monitoring of the regeneration process, and thus improves the operation of the internal combustion engine overall.
In a further refinement of the method according to the invention, in an operating state of the motor vehicle and/or of the internal combustion engine which is assigned to an active regeneration of the particle filter, the filtering operation is carried out when determining and/or processing the particle filter charge variable with a higher cut-off frequency and/or smaller attenuation than in an operating state of the motor vehicle and/or of the internal combustion engine which is assigned to a charge of the particle filter. This measure improves the reliability of the evaluation of the pressure signal for the determination of the particle filter charge during the regeneration of the particle filter during which the charge of the particle filter decreases rapidly. When the particle filter regeneration and the associated operating state of the internal combustion engine are terminated, a slowly changing charge of the particle filter occurs again and the abovementioned measure is reversed, i.e. the cut-off frequency of the signal filtering operation is reduced again and/or the attenuation is increased again in operating states in which the particle filter is charged. In this way, the variable which is assigned to the charging of the particle filter is smoothed again to a greater extent, which ensures its reliable interpretation.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
The invention will be explained in more detail below with reference to a drawing and an associated example.